Abstract

A novel silicon-on-insulator (SOI) polarization splitter-rotator is proposed based on mode-evolution tapers and a mode-sorting asymmetric Y-junction. The tapers are designed to adiabatically convert the input TM0 mode into the TE1 mode, which will evolve into the TE0 mode in the wide output arm while the input TE0 mode excites the TE0 mode in the narrow arm. The numerical simulation results show that the mode conversion efficiency increases with the lengths of the tapers and the Y-junction for the output waveguide widths in a large range. This proposed device has < 0.4 dB insertion loss with > 12 dB extinction ratio in an ultra-broad wavelength range from 1350 nm to 1750 nm. With such a broad operating bandwidth, this device offers potential applications for polarization diversity operating across every communication bands. Fabrication tolerance analysis is also performed in terms of the device width variation, the slab height variation and the variation of the upper-cladding refractive index.

Figures (7)

(a) Schematic of the proposed PSR consisting of mode-evolution tapers and a mode-sorting asymmetric Y-junction. (b) Effective indices of the first three modes in a rib waveguide as a function of the waveguide width. The rib waveguide has a 250 nm rib height and 50 nm slab height. The wavelength is 1550 nm in the simulation.

The mode conversion efficiency for the input TM0 mode as a function of Ltp2 for Ltp1 varying from 1 μm (black) to 10 μm (dark yellow), where Ltp3 is set to Ltp1(W3-W2)/(W1-W0). Insets: the mode propagation for TE0 and TM0 modes in the taper at the 1550 nm wavelength when Ltp1 = 10 μm, Ltp2 = 50 μm and Ltp3 = 5 μm.

The minimum Y-junction length required to achieve various levels of mode conversion efficiency from the TE1 mode to the TE0 mode at port 2 as a function of the narrow arm width Wn. The wavelength is 1550 nm in the simulation.

The mode conversion efficiency as a function of the wavelength in the two output ports. The simulation is carried out by 3D-EME and 3D-FDTD methods. The grid size in the FDTD simulation is chosen as Δx = Δy = Δz = 15 nm. The conversion efficiency below −35 dB is not shown.